I haven't given away post it notes myself, although I have received them. They're very useful, so I use them - and it's quite likely I'd pass these on to others too, maybe if I wanted to scribble down some info for them to look at later. The original company who gave me the post it notes therefore gets his URL in front of yet more eyeballs.
I think the main thing is that if you give someone a business card, they'll probably lose it or throw it away. If you give someone something useful, they'll keep and use it. If they later lose it, then there's a good chance that someone else will come along and use it.
Over the years we've given away various things - T-shirts, lighters, pens. More recently we had some bookmarks done at Nikki Pilkington's suggestion.
It's impossible to measure the ROI of offline advertising, but I'd guess that the T-shirts were a waste of money. Nice shirts! But too expensive for any benefit they might have brought us. The lighters went down quite well but everyone else was giving away lighters at that time, and not everyone smokes. The pens were well received, everyone liked them.
I've seen lots of other promotional little freebies - mouse mats, postcards, bottle openers, etc, etc. I think these can often work better than bog standard business cards.
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Using post it notes as marketing?
